The present invention relates to a multilayer film comprising a layer of an aromatic polyester and a layer of a silicone resin, which is useful as a panel material for a liquid crystal display device. More particularly, the invention relates to a multilayer film comprising a layer of an aromatic polyester prepared from a bivalent phenolic compound or its derivative and an aromatic dicarboxylic acid or its derivative and a layer of an organopolysiloxane, and a liquid crystal display device part using the multilayer film.
In recent years, there is lively studied about using a polymer film provided with a transparent conductive layer on its surface as a liquid crystal display panel in place of a conventional display panel using a glass substrate, in compliance with request of a lighter, larger and breakage-resistant display panel.
Representative polymer films usable for this purpose are polyimide and polyethylene terephthalate films. However, the polyimide film has the drawbacks that the transparency is poor and the moisture absorption is high and, therefore, is not suitable for this purpose, though it has excellent heat resistance and dimensional stability. A biaxially stretched polyethylene terephthalate film has excellent properties such as transparency, mechanical property at ordinary temperature and dimensional stability. However, the index of birefringence is large and, therefore, it is not suitable particularly for display which utilizes polarization phenomenon and requires an optical isotropy, e.g. TN (twisted-nematic) mode liquid crystal display. For this purpose, it is studied to use a uniaxially stretched polyethylene terephthalate film, but the film has an optical anisotropy and its optical axis must be strictly accorded with the optical axis of a polarizer used for a liquid crystal display device. Therefore, the workability and yield are very low.
It has been attempted to use transparent films of thermoplastic amorphous polymers called heat resistant engineering plastics as a panel material for liquid crystal display. Representative one is a polyether sulfone (PES) film. The PES film is inferior in organic solvent resistance and moisture permeability, and when used in liquid crystal display, a good transparent conductive layer is hard to be formed and also the resistance to liquid crystal materials is poor.
It is a primary object of the present invention to provide a material suitable for a liquid crystal display panel.
The above and other objects of the present invention will become apparent from the description hereinafter.